docs: def get_group_index(self, data):
          """Get the next groups style's starting line index
  
          :param data: string to parse
          :returns: the index if found else -1
  
          """
          idx = -1
          li = self.get_group_line(data)
          if li != -1:
              idx = 0
              for line in data.splitlines()[:li]:
                  idx += len(line) + len('\n')
          return idx